pyNode with button: any way to find which node the button pressed was on?
It's possible, but you need to set a property or two on your operator so that it can find the value. Eg:

class MyOperator(bpy.types.Operator):
    tree: bpy.props.StringProperty()
    node: bpy.props.StringProperty()
    ...


Then where ever you draw it, set those properties. Eg:

def draw_buttons(self, context, layout):
    op = layout.operator("myoperator.operator")
    op.tree = self.id_data.name
    op.node = self.name
    ...


You can then use those values in the operator to find out where it was called from.